In building wiring, multiway switching is the interconnection of two or more electrical switches to control an electrical load (often, but not always, lighting) from more than one location. For example, this allows lighting in a hallway, stairwell, or large room to be controlled from multiple locations. While a “normal” light switch needs to be only a Single Pole, Single Throw (SPST) switch, multiway switching requires the use of switches that have one or more additional contacts and two or more wires must be run between the switches. When the load is controlled from only two points, Single Pole, Double Throw (SPDT) switches are used. One example of a multiway switch is a three-way switch. Electrically, a three-way switch is a Single-Pole, Double-Throw (SPDT) switch. By correctly connecting two of these switches together, toggling either switch changes the state of the load from off to on, or on to off. The switches may be arranged so that they are in the same orientation for off, and contrasting orientations for on.
FIG. 4 is a block diagram of a conventional three-way switch. Conventional implementations of a three-way switch require all switches to be replaced in case of a device failure. In addition, it requires the installer to know which end is the load versus the supply (slave or master). With the advent of home automation, it would be beneficial to have more capable three-way switches.